1. Field of the Invention
The present invention relates to a display device and a manufacturing method thereof.
2. Description of the Related Art
A display device on which a light emitting element such as an organic electroluminescent element is provided for each pixel is expected to be a display of the next generation. A light emitting element is configured to emit light in a light emitting layer held between a pixel electrode (anode) and a common electrode (anode), the common configuration is to reflect the emitted light at the pixel electrode. In the case of a display device of the top emission type, since emitted light from the light emitting element is extracted from the common electrode side, the pixel electrode is formed as a reflection electrode, and the common electrode is formed as a transmission electrode. In order to enhance light extraction efficiency, it is favorable that the pixel electrode is a reflection film made of a material with high reflectivity.
However, in order to optimize a work function of a hole injection into the light emitting layer, there is a case where an upper surface of the reflection film (a surface that is in contact with the light emitting layer) is covered by an oxide conductive film such as indium tin oxide (ITO) or indium zinc oxide (IZO). Meanwhile, to retain an adhesion to an inorganic insulating film that is a base layer of the pixel electrode, there is a case where the oxide conductive film is provided on a lower surface (a surface that is in contact with the inorganic insulating film) of the reflection film (Japanese Unexamined Patent Publication No. 2007-317606).
When the pixel electrode is formed, for example, when a laminated film made of an ITO film, Ag film and an ITO film is patterned by mixed acid, an etching residue or a remainder of Ag might be generated. This is caused because nitrogen monoxide gas generated by a reaction of the mixed acid and Ag is attached to a surface of the Ag film, and a passivation of the surface of the Ag film in etching liquid occurs.
Therefore, there is a problem that neighboring pixel electrodes are short-circuited since the patterning by the mixed acid is not enough. As a space between pixel electrodes gets smaller due to an enhanced image definition, the etching residue and the remainder of Ag are more likely to be generated. Further, since the adhesion of the Ag film to the inorganic insulating film is low, when the Ag film is not covered by the ITO film the adhesion of the pixel electrode to the base layer gets lower.
Japanese Unexamined Patent Publication No. 2007-317606 discloses sealing the top, the bottom, and the periphery of the AG film by the ITO film, to thereby shut the Ag off from an organic material and prevent a generation of gas due to a reaction of the Ag and the organic material. Accordingly, since the Ag film is covered, the pixel electrode has a high adhesion to the base layer, and the problem that the present invention tries to solve does not exist here at all.